Piezoelectric crystal holder



LS ECH HOOP L l i? n.554?

sept. 11, 1962 INVENTOR. JOHN B LORD his ATTORNEYS.

United States Patent O 3,054,004 PIEZGELECTRIC CRYSTAL HGLDER John B. Lord, Silver Spring, Md., assignor to Vitro Corporation of America, New York, N.Y. Filed .inne 24, 1957, Ser. No. 667,438 8 Claims. (Cl. S10-9.4)

This invention relates -to piezoelectric crystal holders and, more particularly, to holders for such crystals responsive to sound waves to generate potentials.

Crystals nd wide use in the detection of sound waves. In performing this function, the crystals must be mounted in a lsuitable holder that will not .only protect and seal it but will `also afford electrode means to transmit potentials therefrom. In one arrangement, a crystal is mounted to -be scanned in what may -be termed a Sokolotf type acoustic image cathode ray tube, such as shown in U.S. Patent No. 2,164,125. The screen or yface of such tubes may receive a crystal in a variety of ways. However, it is desirable to scan one crystal surface directly by the electron beam. Attempts to attach the crystal to an inner metallic faceplate of the cathode ray tube have not been entirely successful because of diiculties in achieving a uniform bond.

The present invention overcomes the above discussed problems by providing a sealed crystal holder that securely positions the crystal and provides a uniformly bonded electrode thereon. To this end, a crystal is disposed at an opening in a desired member, such as the face of a cathode ray tube. Subsequently, a layer of metal is deposited on the outer crystal surface and the holder portions contiguous therewith to secure it to the tube face. The metal layer effectively seals the crystal in the holder and functions as one crystal electrode of high uniformity intimately bonded to the crystal.

In one embodiment of the invention, shoulders in the opening support one side of the crystal, the opposite side being flu-sh with the holder surface and receiving the deposited layer of metal. If desired, the initial metal layer may be vacuum deposited Iand subsequently, a further layer may be deposited by electroplating or electroless plating to achieve greater mechanical strength.

These and further advantages of the invention will be more readily understood when the following description is read in connection with the accompanying drawings, in which:

FIGURE l illustrates a cathode ray tube, partially broken away, incorporating a piezoelectric crystal held in accordance with the principles of the present invention;

FIGURE 2 is a fragmentary section, greatly enlarged, of the face of the cathode ray tube illustrated in FIG- URE l showing in detail the crystal mounting;

FIGURE 3 is another fragmentary section illustrating a modified crystal holder embodying the inventive concept; and

FIGURE 4 is a further fragmentary section, greatly enlarged, of another modification of the invention.

Referring to a typical embodiment of the invention in greater detailV with particular reference to FIGURES 1 and 2, 'a cathode ray tube 10, operating in accordance with the principles lset `forth in the above-referred to Sokoloff Patent No. 2,164,125, includes a tube face 11 preferably formed by a metal sheet. An opening 12 in the tube face 11 incorporates a shoulder 13 supporting on its outer side a piezoelectric crystal 14, and on its inner side a collector grid 15 which receives electric charges representative of the oscillations excited by sound waves impin-ging on the crysta-l14, asis well known in the art.

After the crystal 14 has been inserted in the opening 12 with its outer surface flush with the edges thereof, a metal layer 16, greatly exaggerated in thickness in the drawings for clarity, is deposited in any desired manner on the crystal 14 and the portions of .the outer surface of the tube face 11 contiguous thereto. Conventional vacuum deposition of the metal layer will provide satisfactory results. If necessary for mechanical strength, a further metal layer 17, also greatly exaggerated in thickness in FIGURE 3, may be depoisted over the layer 16 by electroplating or conventional electroless catalytic deposition methods.

The metal layer 16 forms one electrode for the crystal 14 against which a metal member may be urged for testing, in accordance lwith the methods described in the above-referred to Sokoloif patent. Vacuum deposition of the layer 16 has been found preferable because it forms an excellent bond between the crystal material and the deposited metal layer. Moreover, such deposition minimizes problems of gas inclusions and voids in the layer 16. Obviously, the metal layer 16 holds and seals the crystal 14 securely in the opening 12. Therefore, completion of the cathode ray tube 10 including process# ing at elevated temperatures to evacuate it to ya high degree will not affect the crystal holder.

An exemplary embodiment of the invention includes a nickel tube Vface in which is mounted a crystal lformed of polycrystalline ybarium titanate. After positioning the crystal in the opening 12, chromium is vacuum deposited according to conventional methods on the cry-stal and holder to form a layer of metal 16, greatly exaggerated in thickness in FIGURE 2 for clarity, on the order of from .0001 inch to .002 inch thick. Subsequently, an additional chromium layer 17 on the order of from .O01 inch to .250 inch thick may be electroplated on the initially deposited layer, as shown in FIGURE 3, to alford added -strength to the unit, if desired.

The holder may initially be in the form of a nickel plate that after fabrication may be fastened by brazing, for example, to the rest of the cathode ray tube envelope.

The dimensions of the layers 16 and 17 are exemplary only and in this regard, it will be understood that they will be determined by the strength required and the crystal resonance, the latter being of more importance when maximum response must be attained.

Referring to FIGURE 4, a modified crystal holder includes an opening 12a in the tube face 11. In this holder, the crystal 14 rests against the inner wall of the tube face 11. The metal layers 16 and 17, deposited through the opening 12a, hold the crystal in position and seal the cathode ray tube. Of course, the layer 17 may be omitted if desired.

The principles of the invention are also applicable to crystal holders for use in liquids where a crystal must be mounted in one wall of a liquid iilled tank, for example. In this instance, a section of the Wall, preferably a demountable section, may be nickel, a quartz crystal may be mounted in a recess therein, and chromium may be vacuum deposited on the crystal and holder to secure and seal the crystal in the wall.

Obviously, other mechanical configurations, metals and crystals may be utilized, the above examples being illustrative only. When elevated temperatures Will be encountered such as in the processing of cathode ray tubes, the coefficient of expansion of the holder and deposited metals should be similar to prevent cracking. Moreover, the deposited metal must be one that will form a good bond with the crystal material. Finally, the combination of crystal material and deposited metal layer must have sufficient strength to withstand any pressure differential across the holder and also provide vacuum integrity for the completed unit.

It will be understood that the above-described embodiments of the invention are illustrative only and modications thereof will occur to those skilled in the alt.

Therefore, the invention is not to be limitedy to the speciiic apparatus disclosed herein.

I claim:

1. A method of mounting a piezoelectric crystal in a holder comprising the steps of positioning the crystal to close an opening in the holder, and depositing a continuous metal layer on one crystal face and on portions of the holder surface contiguous thereto covering the entire line of abutment between the one crystal face and the contiguous portions of the holder to secure and seal the crystal to the holder with its other face exposed and to provide one electrode therefor.

2. A method of mounting a piezoelectric crystal in a holder comprising the steps of positioning the crystal to close an opening in the holder with one crystal face coplanar with a surface of the holder, and depositing a continuous metal layer on the one crystal face and on portions of the holder contiguous thereto covering the entire line of abutment between the one crystal face and the contiguous portions of the holder to secure and seal the crystal to the holder and provide one electrode therefor.

3. A method of mounting a flat-faced piezoelectric crystal in a holder comprising the steps of disposing the crystal in an opening to close the holder with one crystal face coplanar with a surface of the holder, and vacuum depositing a continuous layer of metal on the one crystal face and on portions of the holder surface contiguous thereto covering the entire line of abutment between the oner crystal face and the contiguous portions of the holder to secure and seal the crystal to the holder and provide one electrode therefor.

4. A method of mounting a fiat-faced piezoelectric crystal in holder comprising the steps of positioning the crystal to close an opening in the holder, vacuum depositing a continuous layer of metal on one crystal face and on portions of the holder surface contiguous thereto covering the entire line of abutment between the one crystal face and the contiguous portions of the holder to secure and seal the crystal to the holder with the other surface exposed and to provide one electrode therefor, and depositing a second metal layer on the vacuum deposited layer.

5. A piezoelectric crystal holder comprising a member formed with an opening, a crystal having two opposite surfaces positioned to close the opening, and a continuous metal layer deposited on the exposed portion of one of the crystal surfaces and on portions of the member surface contiguous to the crystal surfaces, the metal layer covering the entire line of abutment between the one crystal surface and the contiguous portions of the member surface to secure and seal the crystal to the holder with its other surface exposed.

6. A piezoelectric crystal holder comprising a member formed with an opening, a crystal having two opposite surfaces positioned to close the opening, one surface of the crystal being flush with a contiguous surface of the holder member surrounding the opening, and a continuous metal layer deposited on one of the crystal surfaces and on the contiguous portions of the member surface ush with the one crystal surface, the metal layer covering the entire line of abutment between the one crystal and the contiguous member surface to secure and seal the crystal to the holder with its other surface exposed.

7. A piezoelectric crystal holder comprising a member formed with an opening, a crystal having two opposite surfaces positioned to close the opening, a shoulder on the member extending into the opening to support the crystal with its outer surface flush with a contiguous surface of the holder member surrounding the opening, and a continuous metal layer deposited on the outer crystal surface and on the contiguous portions of the member surface flush with the outer crystal surface, the metal layer covering the entire line of abutment between the one crystal surface and the contiguous member surface to secure and seal the crystal to the holder with its inner surface exposed.

8. A piezoelectric crystal holder comprising a member formed with an opening, a crystal having two opposite surfaces positioned to close the opening, the edge of the opening tapering to one of the crystal surfaces and forming therewith an obtuse angle, and a continuous metal layer deposited on the exposed portion of the one crystal surface and on the tapered edge of the opening contiguous to the one crystal surface, the metal layer covering the entire line of abutment between the one crystal surface and the contiguous tapered edge of the opening to secure and seal the crystal to the holder with its other face exposed.

References Cited in the file of this patent UNITED STATES PATENTS 2,159,891 Guerbilsky May 23, 1939 2,392,429 Sykes Jan. 8, 1946 2,463,472 Bach Mar. 1, 1949 2,502,970 Manning Apr. 4, 1950 2,507,770 Claassen May 16, 1950 2,677,064 Hill Apr. 27, 1954 2,759,241 Storm Aug. 21, 1956 2,787,520 Meiners et al. Apr. 2, 1957 2,802,955 Kitterman Aug. 13, 1957 2,817,778 Shepherd Dec. 24, 1957 2,848,890 Sheldon Aug. 26, 1958 UNITED STATES PATENT OFFICE CERTIFICATE 0E CORRECTION Patent Nm @054,004 september 11U 1962 John B., Lord I It ie hereby certified that error appears in the abe-ve numbered petent requiring correction and that the said Letters Patent should read. as corrected below.

. Column 2 line 6I for "depoisted" read deposited --g column 3, line 25, for "in an opening to Close" read to close an; opening in --5 column 3g line 34, after "in" insert a Column 4, line lO, after "crystal" insert Surface' line 49 for "Storin" read Sturm Y l Signed and sealed this lSthQday of January 1963@ (SEAL) Attest:

ERNEST w. SWIDER DAVID L- LADD Attesting Officer Commissioner of Patents 

